Religious affiliation is undergoing major changes in rural Sahelian Africa, with profound consequences for customs that are grounded in traditional belief systems. This study examines the influence of women's religious affiliation on contraceptive use and fertility among the Kassena-Nankana of northern Ghana. Analysis of longitudinal data for women in 1995 and 2003 shows that 61 percent of women changed their religion, with shifts from traditional beliefs to Christianity being dominant. Moreover, women were more likely than men to make such a change. Regression results show that, compared with those who did not change, switching from traditional religion to Christianity or Islam is associated with increased contraceptive use and decreased fertility. The more rapid change in religious affiliation among women than men may have social consequences for the status of women, signaling a trend toward greater autonomy in the family and new aspirations, values, and behavior as evidenced by the proportion of people adopting contraceptives.